This invention relates to a computer type electronic flash device and more particularly to a computer type electronic flash device having a light measuring circuit which controls the light extinguishing time of a flash tube by receiving a reflection light coming from an object to be photographed and reflecting light flashed at the object by the flash tube.
Generally, a light measuring circuit of this type is arranged to normally remain in an inoperative state and to operate concurrently with commencement of flashing by the flash tube. The light measuring circuit produces a flash terminating signal. This signal renders a commutating circuit conductive to turn off a thyristor which is arranged in series with the flash tube and thus forces the flash tube to terminate the flash during the process of its flashing action. Following that, the commutating circuit becomes inoperative and then again becomes operative. However, in the conventional flash devices, the flash terminating signal is continuously produced until the commutating circuit again becomes operative. With the signal continuously produced in this manner, a capacitor which is arranged to supply a light energy to the flash device is short-circuited by the commutating circuit and thus remains uncharged. In addition to such a disadvantage, a DC-DC converter which is disposed in a route connecting a power source battery to the capacitor becomes overloaded. This tends to have heat produced by a circuit resistance.